OTTAWA -- The federal government's proposed new law on medically assisted dying is entering uncharted parliamentary waters, where the only certainty seems to be that it will not come out in the same shape in which it goes in.

Final debate on Bill C-14 begins Wednesday in the Senate, where the government no longer has any control over independent-minded, less-partisan senators who appear determined to amend the controversial legislation.

Among other things, senators are likely to amend the bill to ensure that all grievously ill Canadians are entitled to an assisted death, not just those who are near death.

But no one knows what will happen if the government, which has rejected any substantive amendments thus far, refuses to accept Senate amendments. Will senators acquiesce? Will they insist and bounce the bill endlessly back to the House of Commons until they get what they want? Will they actually defeat the bill?

"I don't know -- that's the simplest answer," said Sen. George Baker, who is sponsoring the bill in the Senate.

"I don't know what's going to happen in the Senate. This is a new situation for the Parliament of Canada. There's never been a situation similar to this before."

Conservative Senate leader Claude Carignan was blunt when asked if the bill will be passed by the Senate without amendments.

"Without? Impossible," he said.

Carignan appeared confident there's enough support among Conservative, independent Liberal and independent senators to fix what he sees as the bill's major flaw: the requirement that a person must be near death in order to qualify for medical help to end their suffering. That provision has been slammed by constitutional and legal experts who maintain it flies in the face of the Supreme Court's landmark ruling last year and will inevitably be struck down as unconstitutional.

"That's the type of amendment that we will insist (upon) if the House refuses," he predicted.

Carignan himself is proposing a compromise amendment that would allow those not near death to apply to a court for the right to an assisted death.

Sen. Jim Cowan, leader of the independent Liberals, is proposing to jettison the bill's near-death provisions and replace them with the more permissive wording of the Supreme Court's ruling.

The court directed that medical assistance in dying should be available to clearly consenting, competent adults with "grievous and irremediable" medical conditions that are causing enduring suffering that they find intolerable.

C-14 takes a more restrictive approach, allowing assisted dying only for consenting adults "in an advanced stage of irreversible decline" from a serious and "incurable" disease, illness or disability and for whom natural death is "reasonably foreseeable."

Could the Senate wind up killing the bill entirely, as it did decades ago with the last attempt to legislate abortion in Canada?

"I don't know," Cowan said. "I can only speak for what we're going to do and I think we're doing the right thing in the right way."

The uncertainty over the bill is in large part of Prime Minister Justin Trudeau's own making. As part of a bid to return the Senate to its intended role as an independent chamber of sober second thought, he kicked all senators out of the Liberal caucus several years ago and, since taking office last fall, has set up a new process to appoint only independent, non-partisan senators.

There is no longer any government caucus in the Senate and no levers for the government to try to control what goes on in the chamber.

"We look forward to seeing what suggestions the more independent and less partisan Senate has to make on this important piece of legislation," Trudeau told the Commons on Tuesday.

Just how many amendments senators will propose is unclear. Baker predicted up to 70, Carignan said maybe 10 to 15.

Cowan predicted the amendments will cover a range of issues, including allowing people with competence-eroding conditions like dementia to make advance requests for an assisted death, more stringent safeguards to prevent abuse and more explicit protection for the conscience rights of health care providers who refuse to take part in medically assisted dying.

How long the process will take before the bill is finally put to a vote is unclear. Baker predicted it could go on for weeks; Carignan suggested it may wrap by the end of next week. Some senators hold out hope it could all be over by the end of this week.

While senators continue to deliberate on the bill, the country is now without a criminal law governing medical assistance in dying. In the absence of a law, the procedure will be governed by the eligibility criteria spelled out by the Supreme Court and by guidelines issued by medical regulators in each province.

When the top court struck down the ban on assisted dying, it gave Parliament a year, later extended by four months, to craft a new law. That deadline was Monday.